Core bit



y 13, 1967 c. A. ANDERSON. JR. ET AL 3,333,455

CORE BIT Filed Jan. 29, 1964 INVENTORS MLA-ANuJ-MW ,g Lu: 1 Cite.-

ATTORNEYS United States Patent 3,331,455 CORE BIT Chester A. Anderson, Jr., Hartford, and Leo P. Cote, East Hartford, Conn., assignors to Pratt & Whitney Inc., West Hartford, Conn., a corporation of Connecticut Filed Jan. 29, 1964, Ser. No. 340,891 3 Claims. (Cl. 175403) This invention relates generally to a core bit of the type used for drilling holes in masonry, concrete, reinforced concrete, granite, marble and other similar materials of the same general class used in construction work and the like. Core bits of this general class are known in the art and are usually used with powerdriven, hand-operated tools. It is common practice for the power tools in which such bits are mounted to impart both rotary and impact motion to the bit. Core bits are similar in concept to the machining operation known as trepanning wherein an annular hole is drilled leaving a core of material which is removed substantially intact from the drilled hole.

Present designs of core bits are quite heavy and restrict or interfere with the hammering motion of the tool due to the inertia of the core bit bodies of substantial mass. The weight of known core bits is the result of bit construction utilizing thick-walled bodies having helical grooves along the entire length thereof, the bodies being sufliciently long to reach the full depth of the hole to be drilled. Where holes are to be drilled which are deeper than the normal length of available core bits, extensions or adapters of similar designs are utilized. In some applications, the weight of the core bit reaches such a magnitude that the impact adapted to be transmitted to the bit by the hand-operated power tool becomes a reactive force transmitted to the operator. Also, as may be readily understood, any increase in weight of such components reduces the ease of operation and portability of such devices. The instant invention is an improvement over known devices.

Accordingly, it is an object of this invention to provide an improved core bit of light weight construction.

Another object of the invention is to provide a core bit of such a design that the likelihood of the jamming of a core within the bit is substantially eliminated.

A further object of the invention is to provide an improved core bit whose length can be readily extended without excessively increasing the weight thereof.

Still another object of the invention is to provide an improved core bit having a replaceable cutting element.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

Generally speaking, in accordance with the invention, a cutting element carrying carbide bits consists of a relatively thick-walled cylindrical element having external spiral flutes for the removal of chips and dust normally created during the drilling of masonry and like materials. The longitudinal length of the cutting element is quite short and is secured to a long length of thin-walled tubing whose outside diameter is smaller than the outside diameter of the cutting element, thereby permitting substantial hole clearance for the removal of chips and dust. The thin-walled tubing is preferably removably attached to a shank mounted in the hand-operated power tool and the depth of hole which may be drilled may be readily increased by extending the length of the shank.

The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described and the scope of the invention will be indicated in the claims.

For a fuller understanding of the invention, reference 3,331,455 Patented July 18, 1967 is had to the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a side elevational view of a core bit constructed in accordance with the invention;

FIG. 2 is an end elevational view, as seen from the cutting end, of the core bit of FIG. 1;

FIG. 3 is a sectional view, partially broken away and at an enlarged scale, taken along line 33 of FIG. 2; and

FIG. 4 is a sectional view of a portion of the tubing section, constructed in accordance with a modified form of the invention.

Referring now to the drawing, the cuttting operations are performed by a cutting element indicated generally at 11. Cutting element 11 comprises a substantially cylindrical body portion 12 having a central aperture therethrough. Cut into the exterior surface of body portion 12 are a plurality of spiral flutes or grooves 13 adapted to carry off the chips and dust produced during the cutting operation. The outer edge of body portion 12 from which the flutes extend, is formed as a series of lands 14, the leading edges of which carry carbide cutters 15. The use of carbide cutters for drilling masonry, concrete and other similar materials is, of course, well known. The carbide cutters are preferably brazed to the leading edges of the lands as most clearly shown in FIG. 2. Note that the bit as viewed in FIG. 2 is adapted to rotate in a counterclockwise direction and flutes 13 are generated from the leading edges of cutters 15.

As best shown in FIG. 3, the circular passage through the center of body portion 12 is defined by a short cylinder 16 which thereafter tapers inwardly as indicated at 17 toward the lands, Through use of the taper, a greater securing area is provided for the cutters. It should be noted that body portion 12 is preferably fabricated from a high quality steel.

Body portion 12 is secured on the end of a section of thin-walled tubing 18 Whose outside diameter is smaller than the outside diameter of body portion 12 taken through flutes 13. In order for the bit to be as lightweight as possible, the wall of tubing 18 is quite thin. As an example, a bit adapted to drill a 1%" diameter hole has been constructed, utilizing a 1" outside diameter steel tubing having a wall thickness of only .065". Such a bit has been successfully tested and has proven to have more than adequate strength and torsional rigidity for repeated use, even when drilling through the reinforcing rods of reinforced concrete. Note that the outside diameter of the tubing provides a radial clearance of Ms" in the hole for the unobstructed removal of chips and dust. Addi-' tionally, the flutes 13 in short body portion 12 readily deliver the chips and dust into the clearance area along the exterior of the tubing.

The forward end of tubing 18 is received in the short cylindrical portion 16 of body portion 12 and is preferably brazed in place. As the brunt of the damage to the bit during a drilling operation will be absorbed by cutting element 11, and particularly cutters 15, it may be seen that the cutting element may be readily replaced without the necessity of replacing the entire core bit. Because of its short length and ease of replacement, cutting element 11 is substantially more economical than core bits which, when expended, require replacement of the entire bit. Such bits may be as long as 18", or longer. As mentioned previously, the tapered interior of body portion 12 increases the strength of the body portion in the area of the cutting edges and also provides for the cutting of a core having a diameter substantially smaller than the inside diameter of tubing 18. In this manner, the likelihood of the core becoming jammed in the tubing when the bit is removed from the hole is substantially lessened. In the event that difiiiculty is encountered in removing the core,

a a knock-out hole 19 may be provided through the wall of the tubing. 3

An end cap 21 having a threaded aperture 22 is brazed or Welded to the upper end of tubing 18 for threadedly receiving a shank 23. The shank may have any desired cross-sectional configuration for chucking in the powerdriven, hand-operated tool. To threadedly secure shank 23 in end cap 21, a pair of axially aligned holes 24 may be provided through the wall of tubing 18 for receiving a bar t'herethrough which may be gripped to rotate the tubing and end cap with relation to the shank. This, of course, will also be utilized in disconnecting the bit from the shank. In order to drill holes of greater depth, it is only necessary to increase the length of shank 23 and thus a single bit may be used to drill holes of almost any practicable depth. A composite assembly for drilling deep holes constructed in the aforementioned manner will be substantially lighter than known devices which utilize long body portions of substantial mass.

For certain sizes, it has been found desirable to construct the end cap as an integral part of the tubing section as shown in FIG. 4. Tubing 26 is similar to tubing 18 except that it is provided with heavy section 27 provided with a threaded aperture 28 similar to threaded aperture 22. The manner of attachment of tubing 26 to a shank 23 would be as heretofore described.

In starting holes in masonry material, bits of this type tend to walk off the material. Starting bits have been developed to overcome this. A starting bit is usually inserted into the end of the core bit and remains in place during the drilling of the smaller starter hole and until the core bit'has commenced the drilling of the larger hole. Thereafter, the starting bit is removed. Cutting element 11 is provided with a plurality of seats 25 cut into the interior wall of body portion 12 commencing at lands 14 as shown in FIGS. 2 and 3. The seats are of sufficient depth .to securely hold and drive the starting bit.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above article without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. A core bit comprising a relatively long section of thin-Walled cylindrical tubing having a smooth outer surface, a relatively short body portion having a substantially cylindrical exterior surface and defining at one end thereof an internal shoulder receiving an end of said tubing in coaxial alignment therewith, said cylindrical tubing having a diameter less than the diameter of said body portion so as to provide clearance therebehind, a plurality of circumferentially spaced cutters having leading edges secured to the other end of said body portion, the exterior surface of said body portion having defined therein a plurality of spiral flutes extending the entire length of said body portion and providing communication between the cutting end of said body portion and said clearance therebehind,

said flutes being generated from said leading edges of said cutters in such manner that 'said leading edges directly communicate with said flutes, said body portion having interior walls defining a tapered bore providing communication to the interior of said tubing, the lesser dimension of said tapered bore being at said other end of said body portion.

2. The core bit of claim 1 further defined in that said body portion has seats defined in the interior walls thereof to secure a starter tool therein.

3. The core bit of claim 1 further defined in that said tubing has a pair of diametrically opposed apertures defined therein adapted to receive a bar therethrough.

References Cited UNITED STATES PATENTS 1,271,396 7/1918 Walker 175-403 2,499,543 3/1950 Townsend 175-387 X 2,730,335 1/1956 Lamprecht 175-403 2,761,440 9/1956 Schwab 20 2,856,157 10/1958 Chapin --403 2,858,109 10/1958 Tengberg 175386 2,918,260 12/1959 Tilden 175403 HAROLD D. WHITEHEAD, Primary Examiner. 

1. A CORE BIT COMPRISING A RELATIVELY LONG SECTION OF THIN-WALLED CYLINDRICAL TUBING HAVING A SMOOTH OUTER SURFACE, A RELATIVELY SHORT BODY PORTION HAVING A SUBSTANSTIALLY CYLINDRICAL EXTERIOR SURFACE AND DEFINING AT ONE END THEREOF AN INTERNAL SHOULDER RECEIVING AN END OF SAID TUBING IN COAXIAL ALIGMENT THEREWITH, SAID CYLINDRICAL TUBING HAVING A DIAMETER LESS THAN THE DIAMETER OF SAID BODY PORTION SO AS TO PROVIDE CLEARANCE THEREBEHIND, A PLURALITY OF CIRCUMFERENTIALLY SPACED CUTTERS HAVING LEADING EDGES SECURED TO THE OTHER END OF SAID BODY PORTION, THE EXTERIOR SURFACE OF SAID BODY PORTION HAVING DEFINED THEREIN A PLURALITY OF SPIRAL FLUTES EXTENDING THE ENTIRE LENGTH OF SAID BODY PORTION AND PROVIDING COMMUNICATION BETWEEN THE CUTTING END OF SAID BODY PORTION AND SAID CLEARANCE THEREBEHIND, SAID FLUTES BEING GENERATED FROM SAID LEADING EDGES OF 